The present application relates to a light-emitting element.
FIG. 7 is a side sectional view diagrammatically illustrating the rough configuration of a light-emitting diode which is an example of a light-emitting element. This example shows a configuration example of a substrate-side light extraction light-emitting diode.
The light-emitting diode illustrated in FIG. 7 includes a laminated body on a substrate 11 made of a transparent material. The laminated body includes a semiconductor layer 12 and light-emitting functional layer 13 of a first conductivity type (e.g., n type) and a semiconductor layer 14 of a second conductivity type (e.g., p type). This laminated body provides a structure called a p-n junction using semiconductors.
It should be noted, however, that the first conductivity type semiconductor layer 12 is partially exposed rather than being entirely covered by the light-emitting functional layer 13 and second conductivity type semiconductor layer 14. A first conductivity type electrode 15 has continuity with the exposed portion. The first conductivity type electrode 15 functions as a cathode.
On the other hand, a second conductivity type electrode 16 is formed on the second conductivity type semiconductor layer 14 and has continuity with the same layer 14. The second conductivity type electrode 16 includes a second conductivity type first electrode 16a and a second conductivity type second electrode 16b. The second conductivity type first electrode 16a is capable of functioning as an optical reflecting film. The second conductivity type second electrode 16b is capable of functioning as a contact portion for bump interconnection. The second conductivity type electrode 16, made up of the two electrodes 16a and 16b laminated one on top of the other, functions as an anode.
In the light-emitting diode configured as described above, the portion having the p-n junction structure emits light when a forward voltage is applied from the second conductivity type electrode 16 serving as an anode to the first conductivity type electrode 15 serving as a cathode. That is, the quantum well structure of the light-emitting functional layer 13 is excited by the injection of a current, causing the entire surface of the laminated body including the light-emitting functional layer 13 to emit light.
Incidentally, increasing the lamination area of the light-emitting functional layer 13 is an effective approach for providing more brightness (enhancing the intensity) of light extracted from the light emitting diode. That is, it is effective to increase the area of the light-emitting functional layer 13 covering the first conductivity type semiconductor layer 12 and reduce the area of the exposed portion not covered by the same layer 13.
In the meantime, as for the first conductivity type electrode 15 which has continuity with the exposed portion of the first conductivity type semiconductor layer 12, at least a given area of the same electrode 15 must be exposed outward for bump interconnection.
In order to achieve compatibility between these contradictory requirements, a proposal has been made suggesting that an insulating layer 17 should lie between the laminated body including the light-emitting functional layer 13 and the first conductivity type electrode 15 (refer, for example, to Japanese Patent No. 4172515). Thanks to the mediation of the insulating layer 17 and the overlapping of the first conductivity type electrode 15 on the same layer 17, such a configuration provides a bump interconnection area in the first conductivity type electrode 15 while achieving brightness as a result of increased area of the laminated body including the light-emitting functional layer 13.